Common industrial methods for producing styrene typically include separation and purification processes such as distillation to remove unwanted impurities. Unfortunately, purification processes carried out at elevated temperatures result in an increased rate of undesired polymerization. Distillation is generally carried out under vacuum to minimize loss of monomer.
Furthermore, it is well known that styrene monomers readily polymerize when heated. Heat polymerization is rapid. In fact, polymerization increases with increasing temperature. This polymerization is undesirable during many stages of the manufacturing, processing, handling, storage and use of styrene monomers, as it results not only in the loss of desired monomer end-product, but also in the uses of production efficiency caused by polymer formation and/or agglomeration of polymer on process equipment.
To minimize this problem, free radical inhibitors consisting of nitrated phenol-based retarders have been used to inhibit the polymerization. These reagents are typically added prior to the distillation. However, these nitrated phenol-based retarders can be toxic. Thus, there exists a strong need for a green inhibitor that provides an effective means of preventing polymerization.